Which version of Acrobat with updates do you have?
Which version of FireFox do you have?
I am using Acrobat X 10.1.2 FireFox 9.0.1. Adobe adds Adobe Acrobat 10.1.2.45 add-on for Netscape and FireFox. I can print to Adobe PDF and use the Convert to PDF from FireFox on Windows XP with no problems.